Wireless cellular subscriber terminals are generally required to register a valid subscriber identity, for example, an International Mobile Subscriber Identity (IMSI), with the cellular network before establishing communications sessions. Terminals not having a valid subscriber identity may, however, initiate emergency calls, for example, by dialing “911” in the United States.
U.S. Patent Application Publication No. US2002/0111159 A1 discloses assigning a temporary subscriber identity to a terminal having an invalid subscriber identity to permit establishment of an emergency call session over the network between the terminal and an emergency operator. The temporary subscriber identity includes an E.164 call back number (CBN), which is used to identify the terminal when calling the terminal after the original call is dropped.
WO 02/080499A1 discloses assigning an interim international mobile subscriber identity (IMSI) to a GSM GPRS or a Universal Mobile Telephone System (UMTS) mobile subscriber terminal not having a Subscriber Identity Module (SIM) card so that the subscriber terminal may place emergency calls in circuit and packet-switched networks. The interim IMSI is generated on the terminal by an interim identity generator using, among other information, an international mobile equipment identity (IMEI) associated with the subscriber terminal in the absence of a SIM card. In the network, a user identity module detects the presence of the interim subscriber identity and routes the interim identity to an interim Home Location Register (I-HLR), which is different than the conventional HLR.
Nokia recently proposed revising the Third Generation Partnership Project (3GPP), which comprises several UMTS standardization areas, to enable network identification of attach requests for emergency sessions in Generalized Packet Radio Resource (GPRS) networks. Particularly, Nokia proposed modifying 3GPP, Section 6.5 “GPRS Attach Function”, to require mobile stations (MS) to provide an emergency connection indicator to the network if the attach procedure was initiated for an emergency session. Under the Nokia proposal, the network and particularly the Serving GRPS Support Node (SGSN) must not reject an attach request having an emergency connection indicator. The Nokia proposal supports mobile stations that re-attach to the network prior to each new communication session. Under the Nokia proposal, attachment requests for non-emergency sessions do not include the emergency connection indicator.
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with the accompanying drawings described below.